This invention relates to snubbers or shock absorbing mechanisms of the type which are used to protect portions of power plant or process industry piping and equipment. In particular, said snubbers are used to protect piping and equipment by resisting the acceleration and relative motion of same under earthquake conditions and other dynamic loadings associated with the operation of extensive piping installations. The relative motion controlling device of this invention also provides freedom of movement of the piping during normal operating conditions such as thermal expansion and contraction.
While mechanical snubbers employing telescoping elements and having an inertia mass actuated braking scheme have been available in the prior art, they have not to date been able to provide the advantages of this invention. With this invention, relative velocity is limited and controlled so that sudden destructive stops are avoided if the snubber elements reach their maximum extent of travel and the braking force generated by the device is proportional to the external forces impressed thereon.
In this invention reinforcement of the primary braking is provided by the use of velocity sensitive brakes which are applied when the elements are separating or moving towards each other above a given velocity. The velocity sensitive brake means of this invention not only provides braking in its own right, but also as applied in this invention creates a sustaining action that causes the primary brakes to be applied with a force proportional to the relative velocity of said telescoping elements.
In this invention a new and improved high gain primary braking system is provided which uses multiple braking contact areas and interactive feedback of same to create a controllable and predictable gain in excess of expected stable values. In this invention a secondary mass element is used to provide sensitivity and response of the self-actuating braking system to frequencies of about 3 HZ and thus limit displacement of said elements and provide protection in the high energy-low frequency spectrum of seismic activity.
Thus the present invention with the advantages as disclosed herein is particularly useful for restraining and controlling excessive motion of piping and equipment in nuclear power plants should such piping and/or equipment be subjected to an earthquake or system induced dynamic loading that could cause pipe rupture or equipment damage as a result of excessive acceleration and/or relative motion.